The present invention relates to electric motors, and more particularly to bonding apparatus for electric motors.
Permanent installation of hydromassage bathtubs and equipment associated with the hydromassage bathtubs (e.g., recirculating pumps, lights, heaters, controls, air blowers) generally requires compliance with a number of installation standards. The installation standards may include standards such as those provided by National Electric Code (xe2x80x9cNECxe2x80x9d) (e.g., NEC Article 680), Underwriters Laboratories, Inc. (xe2x80x9cULxe2x80x9d) (e.g., UL Standard 1795) and local authorities (e.g., municipal statutes that are often based on the national standards provided by NEC and UL). Standards relating to bonding often require that devices or conductive materials (e.g., metal) located within a distance of the hydromassage bathtub or other devices that are covered by the standards (i.e., in the bonding area) be bonded together to form a bonding grid of the bonding area.
The purpose of forming a bonding grid is to eliminate the potential for an electrical energy differential (i.e., shock hazard) in the bonding area. The bonding grid acts as a path of less resistance than does the path of resistance provided by a human and/or an animal (e.g., cat or dog) located in the bonding area. Any stray electrical energy inside the bonding area is therefore conducted through the bonding grid instead of through the human and/or the animal located in the bonding area.
Bonding apparatus for bonding an electric motor to a bonding grid are generally known. Typically, the bonding apparatus bonds the electric motor to a bonding conductor which is part of the bonding grid. The bonding conductor includes a solid eight (or larger) gauge bare copper wire. The conductor generally does not require use of insulation or a conduit because the conductor does not carry electrical energy under normal operating conditions (i.e., the bonding conductor is only utilized when an electrical energy differential is present in the bonding area). Existing bonding apparatus, such as a bonding lug apparatus 10 illustrated in FIGS. 1A-B and 2A-C, require that a bonding conductor 14 be passed through an aperture 18 in a bonding lug 20 and then bonded to the bonding lug 20 by tightening a threaded fastener or screw 22 down upon the conductor 14 such that the conductor 14 is captured between the bonding lug 20 and the bottom 26 of the screw 22. The screw 22 is threaded into an aperture or opening 28 in the lug 20. Existing bonding apparatus are commonly formed of copper or copper alloy.
As is illustrated in FIGS. 2A-C, the bonding lug 20 may be connected to an electric motor 34 on the housing 38 of the motor 34 using a threaded fastener or screw 42. When properly installed, the conductor 14 is electrically coupled to the bonding lug 20 and the bonding lug 20 is electrically coupled to the housing 38. Generally an adequate electrical coupling is formed between the conductor 14 and the bonding lug 20. The electrical coupling may be formed via direct contact between the conductor 14 and the bonding lug 20 and/or via indirect contact through the screw 22. The screw 22 is formed of an electrically conductive material and when the screw 22 is tightened down on the conductor 14 an electrical coupling is formed between the conductor 14 and the screw 22. The screw 22 is electrically coupled to the bonding lug 20 through the interaction between the threads of the screw 22 and the corresponding threads in the aperture 28 of the bonding lug 20.
The contact between the bottom of the bonding lug 20 and the housing 38 may provide some degree of electrical coupling, however, the contacting surfaces of the bonding lug 20 and/or the housing 38 may include paint and/or other contamination that can diminish such electrical coupling. The paint and/or other contamination may additionally affect the degree of electrical coupling between the screw 42 and the bonding lug 20 as well as the direct contact between the conductor 14 and the bonding lug 20 discussed above.
The screw 42 is utilized to electrically couple the bonding lug 20 to the housing 38. Typically, the bonding lug 20 includes an aperture (not shown) through which the screw 42 passes and which is only a clearance aperture. Therefore, passing the screw 42 through the clearance aperture does not provide a reliable electrical coupling between the bonding lug 20 and the screw 42 (i.e., the threads of the screw 42 are not electrically coupled to the bonding lug 20 in a fashion similar to the way the threads of the screw 22 are electrically coupled to the corresponding threads of the aperture 40). If the screw 42 is not electrically coupled to the bonding lug 20 then the bonding lug 20 is likely not electrically coupled to the housing 38.
Accordingly, existing bonding lug apparatus (such as the bonding lug apparatus 10) utilize at least one star washer (not shown) (e.g., a star washer located around the screw 42 between the head 50 of the screw 42 and the bonding lug 20 and/or a star washer located around the screw 42 between the bonding lug 20 and the housing 38). Alternatively, or in addition, the screw 42 can have a serrated head to provide an electrical coupling between the screw 42 and the bonding lug 20 and therefore between the bonding lug 20 and the housing 38. The threads of the screw 42 generally become electrically coupled to the housing 38 when threaded into the housing 38, therefore, the coupling that generally presents a problem is the coupling between the screw 42 and the bonding lug 20. The star washer located between the head 50 and the bonding lug 20 and the serrated head are both designed to increase the reliability of the electrical coupling between the bonding lug 20 and the screw 42. The star washer located between the bonding lug 20 and the housing 38 is designed to increase the reliability of the electrical coupling between the bonding lug 20 and the housing 38. Use of the above techniques typically results in a proper installation.
While installing a motor 34 in a bonding area, the efficiency of the installer is important. Currently, the amount of time it takes the installer to bond the motor 34 to the bonding grid (not shown) includes passing the conductor 14 through the aperture 18 and utilizing the above techniques to ensure all corresponding parts are electrically coupled as required. The installer may pass the entire length of the conductor 14 through the aperture 18 or the installer may cut the conductor 14, pass a portion of the conductor 14 through the aperture 18 and then reconnect the cut portions of the conductor 14 together to form a continuous electrically conductive path. Depending on the amount of time it takes to pass the conductor 14 through the aperture 18, reconnect the cut portions of the conductor 14, and/or perform extra electrical coupling steps, the bonding process may require unnecessary time and effort on the part of the installer.
The invention provides an electric motor having an integrally formed bonding apparatus that allows the installer to quickly and efficiently bond the electric motor to a bonding grid of a bonding area. The integrally formed bonding apparatus is electrically coupled to a bonding conductor of the bonding grid simply by laying the bonding conductor on the housing of the electric motor and tightening down a fastener such that the bonding conductor is captured between the housing and the shoulder of the fastener. The installer does not need to pass the bonding conductor through an aperture, cut and reconnect portions of the bonding conductor to bond the motor to the conductor, or connect a bonding lug to the housing of the electric motor. The speed at which the installer can bond the motor to the bonding grid using the invention saves the installer time and money.
More particularly, according to a method of the invention, a fastener having a head is inserted into an aperture of the housing of the electric motor such that a bonding conductor is captured between the housing and the head. The bonding conductor is electrically coupled to the housing via direct contact between the bonding conductor and the housing and/or via indirect contact through the fastener. An integrally formed surface of the housing prevents the bonding conductor from moving out from under the head.
Further objects of the present invention together with the organization and manner of operation thereof, will become apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings wherein like elements have like numerals throughout the drawings.